The invention relates generally to an apparatus for anchoring and selectively tensioning or relaxing a sheet material on a panel structure, and more particularly to such apparatuses used for anchoring and selectively tensioning and relaxing or releasing a sheet material display on a billboard structure.
Large billboards displaying advertising or public service messages are a common sight along roadways and other areas for communicating messages to the public. One common type of billboard has a front display face that is fourteen feet high and forty-eight feet wide. Although other sizes of billboards are also used, this fourteen foot by forty-eight foot size is especially advantageous for high visibility along roadways and from relatively great distances.
Although effective for communicating advertising or public service messages, the processes of positioning a display message on such billboards, and of replacing one display message with another, have been found to be expensive, time-consuming, and cumbersome. In the past, such display messages were painted or printed on a paper-like sheet of material, which was then cut into strips or sections that could be pasted or otherwise adhered to the front face of the billboard. More recently, large relatively flexible sheets of synthetic materials were developed, typically composed of a reinforced nylon material, onto which the display message was painted or otherwise printed, typically with the use of computer-aided processes. These large synthetic sheet material displays, commonly referred to as "superflex" material, are then rolled onto a large roll, which was then lifted into position using a crane or other suitable lifting apparatuses. The sheet material display is then unrolled onto the front face of the billboard, with the vertical and horizontal edge portions of the sheet material display extending around the edges of the billboard. The edges are then typically anchored and tensioned by way of a number of separate of flexible strip-and-hook mechanisms, which include a wheel-type ratchet mechanism for tightening the strap and thereby tensioning the sheet material display.
The above-described method and apparatus for anchoring and tensioning the sheet material display on the billboard, using the strap and ratchet wheel mechanisms described above, have been found to present a number of significant disadvantages. First, the personnel involved in anchoring and tensioning the display sheet are required to carry a large number of the strap and ratchet wheel mechanisms when climbing onto the rear face of the billboard, frequently at great heights. Secondly, because of variations in the supporting structure for the billboard, there are frequently no conveniently-located portions of the support structure to which the straps can be anchored.
Accordingly, in the case of the large billboards mentioned above, the erection, anchoring, and tensioning of sheet material billboard display frequently takes several hours to accomplish and presents great danger and difficulty to persons performing the task. Also, because one end of the strap and ratchet wheel mechanisms includes a hook that must be inserted through an opening in a bar that is in turn hemmed into the edges of the sheet material, anchoring difficulties are frequently encountered if the holes in the anchoring bar are not located near a support member of the billboard supporting structure. As a result, in such an instance, the opposite end of the strap and ratchet wheel mechanisms must be secured to the supporting structure by way of ropes, cables, wire, additional straps, or the like, which is cumbersome, time-consuming and frequently unsuitable.
In addition to the above disadvantages, the prior anchoring and tensioning devices were frequently inadequate in accommodating expansion and contraction of the billboard sheet material display and maintaining a tight, neat-appearing fit. This is especially important in areas that experience wide temperature variations or in applications where the billboard experiences wide variations in the incident sun exposure.
Accordingly, the need has arisen for a simpler, more uniform, and more convenient apparatus for anchoring, tensioning, and subsequently releasing a sheet material display on a billboard structure. The present invention seeks to meet this need by providing an apparatus that is associated and attached to the billboard and that allows for easily and conveniently tensioning and subsequently relaxing a sheet material display on a billboard structure. In some embodiments of the invention, the apparatus also maintains a proper tensioning force that accommodates expansion and contraction of the sheet material display and thus substantially prevents sagging and wrinkles.
The apparatus according to the present invention includes an elongated base member having a generally U-shaped lateral cross-section, with the base member including a base plate portion and a pair of laterally spaced-apart leg portions protruding from the base plate portion. Each of the leg portions preferably includes a slot formed therein, with the slots on the leg portions facing and opening generally toward one another. In some of the preferred embodiments, the base portion further includes a number of ratchet teeth serially spaced longitudinally therealong, and openings are formed in the base portion for receiving fasteners in order to fixedly secure the elongated base member to the panel or billboard structure. Alternatively, other known devices can be included for fixedly securing the base member to the panel structure.
The anchoring and tensioning apparatus of the invention also includes a clip member having a clip plate portion received within the above-mentioned slots for selective slidable longitudinal movement along the base member, an attachment portion for releasably engaging a portion of the sheet material or an anchoring bar hemmed into the sheet material, and in some embodiments, a pawl portion protrudes from the clip plate portion and is resiliently biased into releasable ratcheting engagement with the ratchet teeth on the base member. Such engagement with any one of the ratchet teeth substantially prevents longitudinal movement of the clip member relative to the base member in a longitudinal direction toward the edge of the billboard when the pawl portion engages one of the ratchet teeth, thus anchoring the sheet material display in a desired, tensioned state. The clip member is selectively movable in an opposite longitudinal direction away from the edge of the billboard relative to the base member in order to serially advance the pawl portion from engagement with one of the ratchet teeth to engagement with an adjacent ratchet tooth, thereby increasing the tensioning of the sheet material. The pawl portion is also selectively releasable in order to disengage from the ratchet teeth in order to then allow movement of the clip member relative to the base member toward the edge of the billboard, thereby relaxing or releasing the sheet material for removal.
In the above-mentioned ratchet version of the invention, the tensioning of the sheet material is accomplished by inserting a screwdriver or other lever-type member through an opening formed in the clip plate portion and into engagement with the ratchet teeth in order to forcibly pry or urge the clip member with a pivoting motion of the lever so as to move the clip member relative to the base member and away from the edge of the billboard. Releasing or relaxation of the sheet material display is preferably accomplished by inserting the screwdriver or other lever member through an opening in the clip plate portion and into engagement with a discontinuity on the pawl portion of the clip member, thus allowing the resilient pawl portion to be forcibly disengaged from the ratchet teeth and allowing the clip member to be moved relative to the base member in longitudinal direction toward the edge of the billboard, thereby relaxing or releasing the tension on the sheet material display.
Furthermore, in the preferred embodiments of the present invention, the attachment portion of the clip member includes a generally hook-shaped end adapted for releasable engagement with the sheet material or with an anchoring member or bar secured to the sheet material. Preferably, the anchoring bar or member includes a groove formed therein for releasably and interlockingly receiving the hook-shaped end of the attachment portion of the clip member. The preferred attachment portion of the clip member is at least partially offset outwardly or rearwardly away from the base member in an area adjacent the hook-shaped end, thus allowing the anchoring bar or member on the sheet material to be disposed between the offset portion and the base member when the hook-shaped end is received within the groove in the anchoring bar or member. This provides clearance for tensioning or relaxing movement of the anchored edge of the sheet material relative to the base member of the apparatus, as well as allowing for convenient engagement or disengagement of the attachment portion with or from the sheet material.
In preferred embodiments of the invention, the clip member is resiliently biased in a longitudinal direction away from the edge of the billboard or other panel structure in order to exert a positive, but resiliently variable, tensioning force on the sheet material. Such resilient biasing feature can be employed in conjunction with the above-described ratcheting feature, or alternately with an anchoring handle or lever member that is pivotally, or otherwise movably attached to, or interconnected with, the anchoring apparatus in order to selectively tighten the sheet material or to release the sheet material by applying a force against the above-mentioned resilient biasing component. In some versions of these preferred embodiments, the anchoring handle or lever is also pivotal, or otherwise movable, in either its tightening or its releasing position, in order to be operated or stored without interference with other billboard components or appurtenant members or devices. Preferably the position and/or the range of longitudinal tensioning of the anchoring and tensioning apparatus is pre-adjustable in order to provide for a wide degree of flexibility in sheet material installation. The anchoring handle or lever member, and/or the clip portion of the clip member, can optionally be elongated, angled, or otherwise configured to minimize interference with other components or members, or to allow for more convenient access by the personnel installing the sheet material on the billboard or other panel structure.
Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.